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A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
The human body produces and destroys 15 million blood cells every second.
Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
In 2012, nearly 24 milliion Americans, aged 12 and older, had abused an illicit drug, according to the National Institute on Drug Abuse (NIDA).
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.